As is well known and understood, one of the problems associated with mobile subscriber accessing systems offering direct call-up is that of interference between users. As is also well known and understood, this results from the utilization in such communications systems of omnidirectional antennas. Attempts at utilizing such antennas with very narrow pulses to reduce the probability of self-interference has been shown to be limited. Use of time division multiple accessing, by itself, has not completely solved the interference problem, as signals from moving transmitters often threaten the channel (or time slot) in which another signal is being received. Interference has especially been found prevalent when a call-up is first initiated, before any synchronized acquisition is first established. Although time division multiple accessing communications systems have been developed where directional antennas have been used (see, for example, my issued U.S. Pat. No. 3,908,088), no such workable implementation has been proposed for the mobile arena where omnidirectional antennas are utilized.